Regenerating forests are important for the maintenance of tropical biodiversity. Forest management in fragments of Atlantic forest in Brazil includes removal of exotic eucalyptus trees that were once part of plantations, in order to reestablish native flora. However, it is unclear how native tree saplings regenerating under former plantations respond to abrupt changes in environmental conditions associated with exotic tree removal. We used leaf carbon isotope composition (δ 13 C) and photosynthetic parameters to evaluate physiological responses of native tree saplings to canopy opening. We analyzed young and mature leaves of the three most representative species of regenerating trees (Byrsonima sericea, Siparuna guianensis, Xylopia sericea) in one secondary forest fragment and three managed areas that form an irradiance gradient (9, 85, 230 and 550 µmol m -2 s -1 ) in Brazilian Atlantic forest.Eucalyptus removal increased photosynthetic CO 2 assimilation and stomatal conductance in

Abstract:Isotopic composition of leaf carbon (δ13C) and nitrogen (δ15N) is determined by biotic and abiotic factors. In order to determine the influence of leaf habit and site on leaf δ13C and δ15N in the understorey of two Atlantic forests in Brazil that differ in annual precipitation (1200 and 1900 mm), we measured these isotopes in the shaded understorey of 38 tropical tree species (20 in the 1200-mm site and 18 in the 1900-mm site). Mean site values for δ15N were significantly lower at the 1200-mm site (−1.4‰) compared with the 1900-mm site (+3.0‰), and δ13C was significantly greater in the 1200-mm site (−30.4‰) than in the 1900-mm site (−31.6‰). Leaf C concentration was greater and leaf N concentration was lower at 1200-mm than at 1900-mm. Leaf δ15N was negatively correlated with δ13C across the two sites. Leaf δ13C and δ15N of evergreen and deciduous species were not significantly different within a site. No significant phylogenetic signal for any traits among the study species was found. Overall, site differences were the main factor distinguishing traits among species, suggesting strong functional convergence to local climate and soils within each site for individuals in the shaded understorey.

No abstract

Estresse luminoso em plântulas de jequitibá-rosa (Cariniana legalis, Lecythidaceae): monitoramento da capacidade de aclimatação fotossintética sob duas intensidades de luz Estresse luminoso em plântulas de jequitibá-rosa (Cariniana legalis, Lecythidaceae): monitoramento da capacidade de aclimatação fotossintética sob duas intensidades de luz Light stress in jequitibá-rosa seedlings (Cariniana legalis Lecythidaceae): monitoring photosynthetic acclimation capacity under two light intensities The knowledge of the capacity for acclimation and establishment of plant species is important for the implementation of management programs and ecological restoration of degraded ecosystems. Ecophysiological studies were performed (gas exchange, chlorophyll a fluorescence and photosynthetic pigments content) to evaluate the effect of light intensity on activity and photosynthetic capacity of jequitibá-rosa (Cariniana legalis Mart. Kuntze). The responses of seedlings subjected to the condition of full sun suggest that direct radiation could be a stressor for this species, affecting their performance, although photosynthetic acclimation with increasing light intensity was observed.

No abstract